The class of polymers of carbon monoxide and olefin(s) has been known for some time. Brubaker, U.S. Pat. No. 2,495,286, produced such polymers of low carbon monoxide content in the presence of free radical initiators, e.g., peroxy compounds. U.K. No. 1,081,304 produced similar polymers of higher carbon monoxide content in the presence of alkylphosphine complexes of palladium as catalyst. Nozaki extended the process to produce linear alternating polymers in the presence of arylphosphine complexes of palladium and certain inert solvents. See, for example, U.S. Pat. No. 3,694,412.
More recently, the class of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon has become of greater interest in part because of the greater availability of the polymers. The more recent processes for the production of such polymers is illustrated by a number of Published European Patent Application Nos. including 121,965, 181,014, 222,454 and 257,663 among others. These processes generally employ a catalyst composition formed from a Group VIII metal salt wherein the metal is palladium, cobalt or nickel, the anion of certain strong acids and a bidentate ligand of phosphorus, arsenic or antimony. In a typical polymerization, the polymer product is obtained as a suspension in a polymerization diluent. In principle, the polymerization is suitably carried out as a batchwise process or in a continuous manner.
Batch polymerization is carried out by introducing the catalyst into a batch reactor containing the monomers and the reaction diluent and which is at the desired polymerization temperature and pressure. As the polymerization proceeds, the pressure drops, the concentration of the monomers in the polymerization mixture drops and the viscosity of the suspension increases. Polymerization is continued until the viscosity of the suspension has increased to the point that continued heat removal becomes difficult. In such a batchwise process, the only variable that remains constant is the temperature. A variation of the batchwise process is the semi-batch production in which the pressure as well as the temperature is kept constant by the addition of monomers to the reactor during the polymerization process.
One of the more important properties of the linear alternating polymers of the invention is their bulk density. This ratio of weight (amount) of polymer per unit volume is important in the production, purification, storage and transportation of the polymers. An increase in bulk density, for example, reflects an increase in the amount of polymer that can be produced in a reactor of specified volume. A polymer of high bulk density retains less liquid per unit weight of polymer during post-polymerization treatment of the polymer in procedures such as washing and filtering. It is known that the bulk density of the polymer product is related to the concentration of the polymer in the polymer-containing suspension of the polymerization process. The maximum polymer concentration expressed in kg of polymer/100 kg of polymer-containing suspension, is approximately 100 times the bulk density of the resulting polymer product. Thus, for example, increase in the bulk density of the polymer product by a factor of 5 will approximately increase by the same factor of 5 the amount of polymer produced in a reactor of any given volume. It would be of advantage to provide a process for the production of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon wherein the polymer product is of relatively high bulk density. A copending U.S. patent application, Ser. No. 235,265, filed Aug. 23, 1988 describes a continuous process for increasing the bulk density of the product. It would be of advantage to provide a batchwise process for increasing the polymer bulk density.